This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A081231 #15 Feb 25 2023 03:08:39
%S A081231 2,8,10,170,24,1520,3482,48,530,48842,3480,80,82,227528,962,4730624,
%T A081231 10610,77563250,1728148040,64080026,168,4190210,8994000,16266196520,
%U A081231 278354373650,224,226,6195120,3674890,139128,115974983600,138274082
%N A081231 Let p = n-th prime of the form 4k+3, take smallest solution (x,y) to the Pellian equation x^2 - p*y^2 = 1 with x and y >= 1; sequence gives value of x.
%H A081231 Vincenzo Librandi, <a href="/A081231/b081231.txt">Table of n, a(n) for n = 1..1000</a>
%e A081231 For n=3, p = 11, x=10, y=3 since we have 10^2 = 11*3^2 + 1, so a(3) = 10.
%t A081231 PellSolve[(m_Integer)?Positive] := Module[{cf, n, s}, cf = ContinuedFraction[ Sqrt[m]]; n = Length[ Last[cf]]; If[ OddQ[n], n = 2*n]; s = FromContinuedFraction[ ContinuedFraction[ Sqrt[m], n]]; {Numerator[s], Denominator[s]}]; Transpose[ PellSolve /@ Select[ Prime[ Range[72]], Mod[ #, 4] == 3 &]][[1]] (* _Robert G. Wilson v_, Sep 02 2004 *)
%Y A081231 Values of y are in A082394. Equals A002350(p). Cf. A082393.
%K A081231 easy,nonn
%O A081231 1,1
%A A081231 _N. J. A. Sloane_, Apr 18 2003
%E A081231 More terms from _Robert G. Wilson v_, Sep 02 2004